In recent years, a technique has been studied in which a state of a subject person such as his/her emotion, presence or absence of his/her feeling of stress or feeling of fatigue, or the like is identified by analyzing various kinds of biological information of the subject person.
There has been proposed a technique for determining a state of the subject person based on, for example, expression, posture or brain waves of the subject person, a signal from an electrocardiograph attached to the subject person, or the like (for instance, see Japanese Laid-open Patent Publication No. 2006-130121; coauthored by Haruyo HAMA, Naoto SUZUKI, Yasuhisa HAMA, “Invitation To Emotional Psychology, Approach To Feelings And Emotions”, first edition, Saiensu-sha Co., Ltd. Dec. 10, 2001, p. 137-174; and coauthored by M. F. Bear, B. W. Connors, M. A. Paradiso, “Neuroscience, Exploring The Brain”, first edition, Nishimura Co., Ltd. Jun. 5, 2007, p. 437-452).
There has been also proposed a technique for determining a feeling of the subject person based on voices or conversation emanated by the subject person (for instance, see Japanese Laid-open Patent Publication No. 2002-91482 and Japanese Laid-open Patent Publication No. 2004-259238). For example, an emotion detecting apparatus disclosed in Japanese Laid-open Patent Publication No. 2002-91482 obtains the amounts of change in an intensity, a tempo and intonation of a voice of the subject person, respectively, and based on the amounts of change, generates signals representing respective emotional states of at least anger, sadness and pleasure. An emotion understanding system disclosed in Japanese Laid-open Patent Publication No. 2004-259238 analyzes a dialogue context so as to understand emotions of a speaking person and a listening person.
In a technique for analyzing data of an electrocardiograph or brain waves of the subject person, an instrument for measuring the brain waves or the like is attached to the subject person in order to detect a state of the subject person. For this reason, this technique can be applied only to a location in which such an instrument is allowed to be set. In addition, in order to detect a state of the subject person based on expression or posture of the subject person, an image captured by shooting a face or an entire body of the subject person is used. For this reason, a technique for detecting a state of the subject person based on the expression or posture can not be applied thereto unless the subject person is within a shooting range of a camera. In contrast to this, a technique for detecting a state of the subject person based on his/her voice is widely applicable since the subject person is allowed to be within a range in which a microphone can collect voices of the subject person.
However, a device disclosed in Japanese Laid-open Patent Publication No. 2002-91482 detects a state of the subject person based on only voices of the subject person. For this reason, even if the subject person has a dialogue with other persons, this device can not take account of a state of the subject person suffering from an influence of the other persons. On the other hand, a system disclosed in Japanese Laid-open Patent Publication No. 2004-259238 converts voices of the dialogue into text information by use of, for example, a voice recognition system, and after that, analyzes the text information. However, if the voice is converted into text, then various kinds of nonverbal information such as intonation or strength of the voice, that are not converted into the text, are adversely lost, and so this system may be unable to accurately detect a state of the subject person.